1. Field of the Invention
This invention relates generally to a positive displacement pump, and more particularly to a dual action piston pump.
2. Description of Related Art
Positive displacement pumps which operate so as to have discharge in one portion while simultaneously having intake in another portion have long been known.
Gedney, U.S. Pat. No. 16,366, entitled "Double-Acting Pump", discloses one such pump having two separate piston and cylinder units operating in this manner.
McIntire, U.S. Pat. No. 208,192, entitled "Force-Pump", discloses a pump operating in this manner having a single piston and cylinder. The piston rod extends from one end of the cylinder.
Boyle, U.S. Pat. No. 4,580,954, entitled "Oscillating-Deflector Pump", discloses a pair of pumps, each having two cylinders and pistons.
The valves or deflectors used in the foregoing devices are generally of the same four way valve configuration.
French Pat. No. 2.226.019, discloses a double acting pump having adjustable frequency and length of stroke. This patent has a sleeve piston which controls operation of the two pump pistons by alternately moving one to close the intake from a hopper and opening the discharge while the other in the opposite mode.
The present dual action pump employs a single, centrally located piston and cylinder with coaxial drive pistons on the opposite ends. Inspection ports permit observation of interior operation and are readily removed for maintenance. The valve spade shifts across pump ports and not across suction and discharge ports providing safer operation.